Hepatitis C virus (HCV) chronically infects 2-3% of the global population, predisposing the patients to chronic liver diseases and liver cancer. The most effective treatment for HCV infection employs a combination of pegylated interferon-alpha (IFN-1) and ribavirin which is only partially effective, costly and requires long-term medical support and follow-up. To combat this major public health threat, a detailed understanding of the viral molecules will greatly facilitate vaccine and anti-viral drug design. The HCV envelope spikes, comprised of heterodimers of the E1 and E2 viral glycoproteins, are important for viral attachment and entry into host cells, and the assembly of infectious virus particles. The E1 and E2 glycoproteins are potential targets for pharmacological and immunological intervention. The long-term objective of this application is to determine the crystal structure of HCV E2 glycoprotein to aid the rational design of anti-viral drugs and vaccines, and to understand the viral entry mechanism at the structural level. The specific aims are (i) to develop methods to produce highly pure recombinant E2 proteins and to characterize their biochemical properties in details;and (ii) to generate a crystal of the recombinant E2 protein as a proof-of-concept for the crystallographic study of HCV E2 glycoprotein. Success in these aims will provide a strong scientific foundation for pursuing the high-resolution crystal structure of E2. PUBLIC HEALTH RELEVANCE: Determination of the crystal structure of the E2 glycoprotein of Hepatitis C virus (HCV) will provide extremely valuable information for drug and vaccine design to combat HCV. The major scientific roadblock is a lack of highly pure and natively folded E2 glycoproteins that will form crystals for X-ray diffraction. The aim of this proposal is to remove this roadblock by developing methods to produce natively folded E2 and by identifying the experimental conditions for its crystallization as a proof-of-concept study for the determination of high-resolution crystal structure of HCV E2 glycoprotein.